The invention relates to a roller lock for releasably fastening a roller in a printing machine, the roller lock having a pressure piece for holding the roller.
In the published German Patent Document DE 36 17 594 A1, such a roller lock is described, wherein the pressure piece is embodied as a locking ring. The locking ring exerts a retaining force on an axle or shaft journal or kingpin of a roller secured in the roller lock, the locking ring pressing on one side of the roller lock against a ball bearing seated on the axle or shaft journal. On the opposite side of the roller lock, a compression spring which generates the retention force is inserted between the locking ring and a bearing body. For a rotation of the locking ring on the bearing body, which is required for opening and closing the roller lock, a given amount of bearing play is required between the bearing body and the locking ring. Due to the bearing play, the locking ring is lifted slightly from the bearing body by the compression spring on its side of the roller lock, as long as there is no contact force acting upon a bale or body of the roller.
It can be assumed, however, that a contact force acting upon the bale or body of the roller is exerted by a cylinder with which the roller is in rolling contact. The bearing body is formed with a unilateral insertion and removal recess, on the side of which the cylinder cannot rest on the roller, because on the side of the insertion and removal recess there must be enough free space to insert or place the roller in the roller lock and to remove the roller. Accordingly, the cylinder can rest on the roller only on the side whereon the compression spring is also located. The contact force exerted by the cylinder on the roller, the magnitude of which exceeds that of the retention force, radially displaces the ball bearing to a slight extent in the roller lock and compresses the compression spring, until the locking ring strikes the side of the compression spring on the bearing body.
When the roller lock, which is under load from the contact force, has assumed this state, a hollow space that receives the ball bearing and is located between the bearing body and the locking ring is widened by a dimension corresponding to the bearing play, and the ball bearing is no longer securely surrounded by the bearing body.
If the cylinder, for example, in the form of a plate cylinder, has a cylinder channel open at the circumference of the cylinder, then each time the roller rolls over the cylinder channel a brief reduction in the positioning force and a relieving of the roller lock occur and, as a consequence, the widened roller lock is pulled together again by the compression spring. Because of the rhythmic loading and relieving of the roller lock which occur when the roller and the cylinder roll on one another, the roller together with the intrinsically xe2x80x9cworkingxe2x80x9d roller lock begin to vibrate, which has an effect upon the printed image.
A roller lock described in the published German Patent Document DE 42 43 657 C2, which has a pressure piece embodied as a hold-down device, and a further roller lock, described in the published German Patent Document DE 195 11 710 C1, which has a pressure piece embodied as a fast-action closure, are unstable under dynamic loads of the roller in a manner similar to the roller lock described in the first reference discussed hereinabove in the published German Patent Document DE 36 17 594 A1.
In the published European Patent Document EP 0 741 009 B1, a printing press with a separable auxiliary bearing for a free end of a floatingly supported pressure roller is described. It is not possible to remove the pressure roller itself from the printing press. Instead, provision is made for removing a sleeve from the pressure roller, which requires loosening the auxiliary bearing. An axle or shaft journal of the free end of the pressure roller carries a roller bearing, which is clamped between a stop and a pressure piece, shown as an abutment, of the auxiliary bearing. The pressure piece, via the roller bearing, exerts a retention force on the axle journal that is generated by a pneumatic cylinder. A contact force exerted on a bale or body of the pressure roller by a counterpressure cylinder, such as an impression cylinder, is directed precisely in the opposite direction from that of the retention force and towards the pressure piece. If the counterpressure or impression cylinder were assumed to have a cylinder channel that the pressure roller rolls over, then, every time the pressure roller would emerge from the cylinder channel, the contact force would rise abruptly, and the roller bearing would consequently lift briefly from the stop, as it overcomes the retention force. The pneumatic cylinder, which is functionally equivalent to a soft gas-compression spring, does not prevent the abutment together with the roller bearing from being forced away from the stop by the pressure roller loaded with the increased contact force. The auxiliary bearing is therefore unstable under dynamic loads and is not suited for sheet-fed rotary printing machines wherein the impression or counterpressure cylinder is formed with at least one cylinder channel for a gripper bar, which could cause vibration of the pressure roller in the auxiliary bearing.
It is therefore an object of the invention to provide a roller lock for releasably fastening a roller in a printing machine, wherein the roller lock is stable under dynamic alternating stresses of the roller.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a roller lock for releasably fastening a roller in a printing machine, comprising a pressure piece for retaining the roller, the pressure piece serving for exerting a retention force on a shaft journal of the roller, the roller having two stops between which a central axis of the roller extends, both a force action line of the retention force of the pressure piece exerted on the axle journal of the roller, and a force action line of a contact force exerted on a bale of the roller being directable through the central axis.
In accordance with another feature of the invention, the roller lock includes a spring for generating the retention force, the pressure piece being loadable by the spring.
In accordance with a further feature of the invention, the roller lock includes a securing device for holding the pressure piece, counter to tension of the spring, in a position wherein the pressure piece is retracted from the stops.
In accordance with an added feature of the invention, the securing device comprises a detent bolt receivable in a detent notch.
In accordance with an additional feature of the invention, the spring is a leg spring.
In accordance with yet another feature of the invention, the pressure piece is a cam.
In accordance with yet a further feature of the invention, the pressure piece has a self-locking contour.
In accordance with yet an added feature of the invention, the roller lock includes a coupling having a coupling half disposed on the axle journal of the roller.
In accordance with yet an additional feature of the invention, the coupling is an articulated joint coupling.
In accordance with still another feature of the invention, the roller lock is formed with a guide face for displacing the roller axially in the direction of said central axis out of a first position and into a second position.
In accordance with still a further feature of the invention, the roller lock includes a rotary bearing for the roller, the rotary bearing being out of coincidence with the pressure piece and the stops in the first position, and coinciding with the pressure piece and the stops in the second position.
In accordance with still an added feature of the invention, in the first position, a rotary bearing of the roller is in coincidence with an insertion and removal recess, and in the second position, the rotary bearing is out of coincidence with the insertion and removal recess.
In accordance with a concomitant aspect of the invention, there is provided a printing machine having a roller lock for releasably fastening a roller in the printing machine, comprising a pressure piece for retaining the roller, the pressure piece serving for exerting a retention force on a shaft journal of the roller, the roller having two stops between which a central axis of the roller extends, both a force action line of the retention force of the pressure piece exerted on the axle journal of the roller, and a force action line of a contact force exerted on a bale of the roller being directable through the central axis.
Thus, the roller lock according to the invention for releasably fastening a roller in a printing machine, having a pressure piece for retaining the roller, calls for both a force action line of a retention force of the pressure piece exerted on a shaft journal of the roller and a force action line of a contact force exerted on a bale of the roller to be directed through a central axis of the roller between two stops of the roller lock.
The force action line of the contact force is indeed offset in the axial direction of the roller with respect to the stops, but viewed in the axial direction (in projection), it is directed between the stops.
A marked advantage of the roller lock of the invention resides in the high stability thereof in the face of alternating dynamic stresses of the roller. The roller lock is therefore especially well suited for an application wherein the roller rolls on a cylinder that has a cylinder channel, and the contact force as the roller rolls over the cylinder channel suddenly decreases and increases again, or wherein the roller rolls on a cylinder (a roller) that in turn rolls on a cylinder having a cylinder channel, and the contact force changes each time the cylinder or roller rolls over the cylinder channel.
For securing the roller in the roller lock virtually vibration-free, a rotary bearing of the roller, a bearing which is mounted on the axle journal, can be fastened between the stops on the one hand and the pressure piece on the other. Then the stops and the pressure piece between them enclose the rotary bearing, in a manner equivalent to a radial three-point bracing. Both the retention force brought to bear by the pressure piece, and the contact force brought to bear by the cylinder press the rotary bearing against the two stops, which are angularly offset from one another and protrude toward an outer circumference of the rotary bearing.
If the contact force drops briefly during the passage of the cylinder channel, the rotary bearing remains held securely in contact with both stops by the pressure piece. Because of this positive fastening of the rotary bearing, the roller is held in the radial direction practically without play or any vibration in the roller lock.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a roller lock for releasably fastening a roller in a printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: